Electronic systems are becoming faster, denser in the number of components, and increasingly complex. Increasing density typically requires greater current which, in turn, requires low resistance interconnection and effective heat dissipation. Higher speed and larger currents require low inductance. Increasing complexity often requires that subassembly boards be mounted and connected onto system boards (“motherboards”). The available space for subassemblies is often limited to narrow strips of board rather than large areas and this in turn limits the choice of subassembly package. Typically subassemblies are connected to system boards by conventional PTH (Plated Through Hole) technology. This technology involves connecting either a vertical or horizontal board to a system board by inserting pins protruding from the subassembly into holes in the system board. The pins are then soldered to secure the subassembly to the system board. Horizontal boards can be mounted to system board by standard SMT (Surface Mount Technology). This involves connecting gull wing leads, “J” leads or a solder ball (BGA) leads by SMT reflow. Vertical subassemblies are normally mounted by PTH technology.
Both the subassemblies and the mother boards are typically printed circuit boards comprised of insulating substrates supporting patterns of conductive leads, mounting pads and circuit components. Such assemblies are now quickly manufactured by a surface mount technology that can precisely place components on mounting pads and efficiently connect them by solder reflow.
Surface mount assembly works well with small components. However subassemblies can be relatively large in area compared with individual components, and in connecting one printed circuit board (e.g. a subassembly board) to another (e.g. the mother board) can present issues of co-planarity. If the two printed circuit boards are not sufficiently co-planar, mounting pads may not touch and solder reflow will not connect. In addition, larger area devices typically require expensive specialized pick-and-place equipment to assemble on motherboards in high volume.
Accordingly, there is a need for improved arrangements to vertically mount subassembly boards using surface mount technology.